Real-Time Environmental TEM Investigation of Perovskite Electrode Degradation in Solid Oxide Cells

Understanding real-time degradation mechanisms at the nanoscale is crucial for enhancing the performance and durability of solid oxide electrolyzers and fuel cells (SOEC/SOFC) components. While conventional post-mortem techniques provide valuable structural insights, they fail to capture the dynamic processes occurring under operational conditions. In this work, we leverage the capabilities of operando environmental transmission electron microscopy (ETEM) to directly visualize and analyze interface degradation in perovskite-based electrodes at the atomic scale. Our approach integrates high-resolution (S)TEM imaging, electron energy loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) with simultaneous electrochemical measurements. A TEM holder with matched heating-biasing MEMS chips enables in situ heating and electrical polarization, while an environmental TEM allows controlled introduction of reactive gases (O2, H2, H2O), simulating realistic SOEC/SOFC conditions. This methodology facilitates real-time tracking of phase transformations, elemental migration, and valence state evolution during operation. Investigations focused on lanthanum-strontium-cobalt oxide (LSC) and lanthanum-strontium-ferrite (LSF) electrodes interfaced with yttrium-stabilized zirconia (YSZ) and gadolinium-doped ceria (CGO) electrolytes. Under polarization in 2.7 mbar O2 at 750 °C, (S)TEM imaging revealed critical structural changes: phase decomposition in negatively biased LSC electrodes and crack formation at the LSC/YSZ interface in positively biased regions. STEM-EELS and STEM-EDS mapping uncovered iron, cobalt, and strontium migration, directly correlating with variations in electrochemical impedance spectroscopy (EIS) measurements. This study highlights the power of ETEM in capturing the dynamic structural and chemical evolution of perovskite electrodes under realistic operating conditions. By correlating nanoscale observations with electrochemical performance, this approach provides unprecedented insights into degradation pathways, paving the way for the design of more robust SOEC/SOFC materials [4].